Knife sharpener



FIG. 1 is a left side elevational view of a knife sharpener in accordance with this design, the right side elevational view is a mirror image thereof;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a cross-sectional view taken through FIG. 1 along the line 6--6; and,

FIG. 7 is a perspective view thereof. 

The ornamental design for a knife sharpener, as shown and described. 